The present invention relates to piston-type flush valves for use on a commode or a urinal and more specifically to a piston-type flush valve having a filter and bypass orifice with multiple filters in fluid flow series.
Piston-type flush valves such as the flush valve shown in U.S. Pat. No. 4,261,545 have used a filtered bypass orifice through the piston assembly. The bypass provides inlet fluid pressure above the piston for closing and then holding the piston assembly on the valve seat after the flush operation. The orifice is sized to allow a predetermined amount of fluid flow through the flush valve before the valve closes. The filter prevents the small bypass orifice from clogging with particulate from the fluid inlet and is configured to allow sufficient fluid to flow through the orifice even after portions of the filter becomes clogged with trapped particulate or sediment.
One disadvantage of the aforementioned flush valve in the ""545 patent is that the filter has a single stage and can allow irregularly-shaped particulates to pass through which may later clog the downstream orifice.
Another disadvantage is that only a limited number of parallel filtering grooves are provided upstream of the orifice. The parallel grooves 78, as shown in FIG. 3 of the patent, are molded perpendicular to the parting line of the mold for the piston cylinder. When this limited number of filtering grooves become significantly clogged with sediment, the flush valve must be disassembled so the filter can be cleaned.
Another disadvantage of the above noted flush valve is that the orifice is a horizontal hole molded through the mid-section of the molded piston cylinder. Therefore, the orifice must be molded using a core pin, which increases the complexity of the molding process. Since the size of the metering restriction in the orifice determines the amount and rate of fluid flow through the flush valve, to change the flow rate, a different piston cylinder with a different size orifice must be provided.
The present invention provides a multiple stage filter and readily replacable bypass orifice for a piston-type flush valve in which the individual openings in the filter are smaller than the restriction in the bypass orifice to prevent the orifice from clogging due to particles in the water.
The present invention provides a plurality of individual filtering slots in multiple concentric arrays upstream of the orifice.
The present invention provides a bypass orifice member in which the size of the metering restriction in the orifice member may be readily changed without changing the piston so as to vary the amount and rate of water that flows through the flush valve during each flush operation.
Other purposes will appear in the ensuing specification, drawings and claims.